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Embryology Flashcards

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1
Q

Embryology definition

A

It is the science that deals with the study of the intra-uterine development of the human body till birth

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2
Q

Embryo

A

From 2nd to 8th week

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3
Q

Foetus

A

From 9th week to 9th month

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4
Q

Teratology definition

A

It is the science that deals with the study of abnormal foetal development causing congenintal malformations.

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5
Q

Gametogenesis in males and females

A

Males —> Spermatogenesis

females —> oogenesis

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6
Q

Purpose of gametogenesis

A

To reduce number of chromosomes from a diploid number to a haploid number
To alter the shape of the germ cell to make it more specialized to its function

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7
Q

Spermatogenesis site, conditions, onset, end, period and hormonal control

A 
It is the process of formation of sperms
Seminiferous tubules which are the structural unit of the testis
Lower than normal body temperature (35)
Starts at age of puberty and doen't end
takes about 64 days 
Controlled by FSH
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8
Q

Stages of spermatogenesis

A

Spermatogonia to primary spermatocyte (by mititic division)
Primary spermatocyte to secondary spermtocyte (by first meiotic division)
Secondary spermtocyte to spermatids (by second meiotic division)(mitotic)
spermatids to sperms through differentiation and maturation

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9
Q

Abnormalities of the sperms

A

Abnormalities in shape
Abnormality in motility
Abnormality in sperm count ::: Oligospermia (<20 million/ml)
Necrospermia (dead sperms)
Azospermia (0 sperms)

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10
Q

Enumerate length & parts of mature sperm

A

Sperm is about 50u and consists of head, neck, middle piece and tail

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11
Q

Mention characters of seminal fluid

A

Geryish, offensive, alkaline watery medium.
Rich in vitamin C and fructose
About 2-4 ml per time

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12
Q

Enumerate source of seminal fluid & its hormonal control

A

Contains spermatozoa and secretions from the prostate, seminal vesicles and bulbo-urethral glands.
Stimulated by LH

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13
Q

Define fertilization & mention its site

A

It is the process of invasion and fusion of the mature sperm with the fully formed ovum to produce a zygote
It occurs in the wide lateral 1/3 of the uterine tube (ampulla)

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14
Q

Enumerate mechanism of transport of sperms

A

The spermatozoa pass rapidly from the vagina into the uterus
Undulating movement of their tails acting as propellers
Contraction of the muscles of the uterus and tube producing suckling action

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15
Q

Enumerate mechanism of transport of ovum

A

The sweeping movement of the fimbriae of the uterine tube with carry the ovum in a stram of peritoneal fluid
Activity of the cilia of the uterine tube
Muscular contraction of the tubal wall

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16
Q

Define capacitation & its mechanism

A

Preperation of freshly ejaculated sperms to be aable to penetrate the ovum
MECHANISM
Removal of the surface coating glycoprotein coat derived from seminal fluid
Unmasking of the glycosyltransferase on the sperm cell membrane

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17
Q

Enumerate acrosomal contents and their function

A

The acrosome contains enzymes
Hyalurinidase: assists in penetration of corona radiata
Zonalysin and trypsin-like substances: needed for digestion of zona pellucida
Acrosin: attached to the inner surface of the acrosomal membrane and helps the sperm cross the zona pellucia

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18
Q

Oogenesis site, conditions, onset, end, period and hormonal control

A

It is the process of formation of mature ova
Coretx of the ovary
Normal body temperature
Starts during fetal life and continues after puberty
ends at menopause
Stimulating factor is FSH

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19
Q

Enumerate results of fertilization

A

Formation of zygote
Restoration of diploid number of chromosomes.
Determination of sex and heriditary characteristcs
Cleavage of zygote

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20
Q

Mention the significance of zona pellucida

A

Once a sperm penetrates, zonal reactions prevents further penetration of other sperms
Keeps dividing cells together during migration
Prevents adhesion to the uterine tube epithelium

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21
Q

Define cleavage & enumerate its stages by time

A

A series of repeated mitotic divisions resulting in an increase in number of cells after fertilization
2 cell stage —> 30 hours after fertilization
4 cell stage —> 40 hours after fertilization
8 cell stage —> 2-3 days after fertilization
16 cell stage —> 3-4 days after fertilization (called morula)

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22
Q

Mention the events occur in first week

A

Fertilisation
Cleavage
Implantation

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23
Q

Mention normal site of implantation

Study These Flashcards
A

Upper part of the posterior wall of the uterus near the fundus in the median plane

24
Q

Mention the abnormal sites of implantation

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A 
Inside the uterus
-Inside the cervix
-At internal os
-Lower down in the body of the uterus 
      -Placenta previa lateralis
      -Placenta previa marginalis
      - Placenta previa centralis
Outside the uterus (Ectopic pregnancy)
    -Abdominal pregnancy
    -Tubal pregnancy
    -Ovarian pregnancy
25
Mention the events occur in second week of fertilization
2 embryonic layers: Epiblast and hypoblast 2 cavities: Amniotic cavity and yolk sac 2 trophoblast layers: Cytotrophoblast and syncytiotrophoblast 2 zones of extra-embryonic mesoderm: Visceral and parietal mesoderms seperated by extraembryonic coelom (later called the chorionic cavity)
26
Mention events occur in 11th & 12th days
The balstocyst is now completely embeded in the endometrium. the endometrium is now called the decidua. The syncytiotrophoblast erodes the decidua and communication between maternal blood sinusoids and lacunae starts the utero-placental circulation Primamry mesoderm is formed and divided into 2 visceral and parietal mesoderms
27
Mention the origin of extra embryonic mesoderm and its division
Extra-embryonic mesoderm is derived from the hypoblast | It is divided into visceral mesoderm and parietal mesoderm seperated by the chorionic cavity
28
Define gastrulation and mention its time
The transformation of the bilaminar embryonic disc to a trilaminar embryonic disc From the 14th to the 19th
29
Define primitive streak and mention its function, fate & anomalies.
By the 15th day, a thickened dark line appears caudally in the midline of the dorsum of the embryonic disc. It results from the rapid multiplication and migration of epiblast cells towards the centre. Function: It actively forms the intra-embryonic mesoderm until about 4th week Significance: determine the direction of the embryo and formation of notochord Fate: After formation of the intra-embryonic mesoderm, it dimishes to become an insignificant structure in the sacrococcygeal region. Anomalies: If it doesn't disappear, it gives rise to teratoma
30
Mention the function and fate of notochord
The notochord is the structure around which the vertebral column forms. It degenerates when the verterbral bodies are formed but remains as the nucleus pulposus It acts as the primary inducer for the formtion of the neural plate may give rise to a tumor called chordoma
31
Define neurulation, its onset & its functions
Onset: 19th day Overgrowth of the ectodrem cells abovethe notochord results in formation of neural plate The neural plate edges are raised and forms the neural folds and the neural groove. The 2 edges fuse together and forms the neural tube and at the site of the union 2 neural crests are formed functions: The cranial part of the tube forms the brain and the caudal part forms the spinal cord.
32
Mention 4 derivatives of neural crest
``` Melanocytes Cells of suprarenal medulla Autonomic ganglion cells Dorsal root ganglion cells Cranial sensory ganglion cells Neurolemmal cells ```
33
Enumerate number of somites and its differentiation
The total number of somites is 42-44 pairs. Each somite is defferentiated: -Ventromedial(Sclerotome) which forms the axial skeleton -Dorsolateral (Dermomyotome) which is differntiated furthur to -Myotome that forms the striated skeletal muscles - Dermatome which forms the dermis of the skin
34
Mention the divisions of lateral plate mesoderm and their derivatives
The lateral plate is divided into: - Intra-embryonic somatic mesoderm that forms the muscles of the thoracic and abdominal walls - Intra-embryonic splanchnic mesoderm forms the smooth muscles of the thoracic and abdominal viscera - The intera-embryonic coelum develops the body cavities: - Pleural cavity - Pericardium - Peritoneum
35
Enumerate 4 derivatives of the ectoderm
The centra nervous system The peripheral nervous system The sensory epithelia of the nose, ear and eyes The epidermis of the skin including the hai and nails Pituitary gland The subcutaneous and sweat glands
36
Enumerate 4 derivatives of the endoderm
Initially, epithelial linning of primitive gut Epithelial linning of respiratory tract Epithelial linning of urinary bladder and urethera Epithelial linning of tympanic cavity and auditory tube The parenchyma of the thyroid, parathyroid, liver and pancreas The reticular stroma of tonsils and the thymus
37
Enumerate 4 derivatives of the mesoderm
Paraxial mesoderm forms the skeletal muscles, the axial skeleton and the dermis of the skin The intermediate mesoderm forms the urogenital system (kidney, ureter), adrenal cortex, gonads, Vagina, uterus and uterine tubes
38
Mention directions of folding & their causes
Cephalo-caudal direction: caused by rapid growth of neural tube Lateral direction: Caused by rapid growth of somites
39
Enumerate results of folding
Formation of head bulge Formation of primitive mouth (stomodium) which is a depression between the head bulge and the thoracic bulge Formation of the thoracic bulge (pericardial bulge) Formation of gut tube (future GIT) and definitive yolk sac Formation of the vitello-intestinal duct Expansion of the amniotic cavity. Formation of the cloaca
40
Mention sources of amniotic fluid
- In early stages: from the amnioblasts - later: when the kidney develops, urine is added to the amnion - Some may be formed as a transudation from the placenta
41
Enumerate functions of amniotic fluid
Permits symmetrical external growth of the embryo Prevents adherence of the amnion to the embryo Cushions the embryo against injuries Halps to maintain an even temperature around the fetus Enables the fetus to move freely Aids in musoskeletal development Helps to dilate the cervix during labour and sterilize the vagina
42
Mention anomalies of amniotic fluid
If the amnion doesn't ruptue, the fetus is born inside the amniotic sac Premature rupture of the amniotic membrane Oligo-hydramnios: The amount of fluid is less than 400cc. Caused by renal agenesis or obstruction of the urethra Poly-hydramnios: The amount of fluid exceeds 1.5-2 liters. Can be caused by -In multiple pregnancies -Idiopathic (35%) -Maternal diabeties (25%) -Anencephaly -Esophageal atresia
43
Mention functions of yolk sac
Nutrition of blastula at early stage of development (2-3 week) Formation of blood cells at early stage of development (3-6 week) Shares in formation of gut at 4th week Shares in formation of intestinal mucosa from the roof of yolk sac Shares in the formation of gonads by the primordial germ cells that appears at the 3rd week
44
Define allantois and its fate
It is a finger like process arising from the secondary yolk sac to the connecting stalk FATE: During formation of urinary bladder, it changes to form a blind tube called the urachus that connects the urinary bladder to the umblicus After birth, it changes to form a fibrous band called median umblical ligament that suspends the urinary bladder to the umblicus
45
Mention abnormalities of allantois
Urachal fistula Urachal sinus Urachal cyst
46
Enumerate contents of umbilical cord
``` 2 Umblical arteries 1 Umblical vein Vitello-intestinal duct Definitive yolk sac Allamtois in its proximal part Intestinal loop between 6 weeks to 3 months (physiological hernia) ```
47
Mention anomalies of umbilical cord
``` Anomalies in its length Anomalies of shape (knots) Anomalies in number Anomalies in the site (Physiological umblical hernia) Anomalies in attatchement to the placenta -Normal in the centre -To the edge : battledore placenta -To the membrane: placenta velamentosa ```
48
Define connecting stalk and its fate
49
Define decidua and mention its parts
``` Decidua is the endometrium after the implantation of the blastula Its parts: -Decidua basalis -Desidua capsularis -Desidua parietalis ```
50
Define chorion and enumerate types (degrees) of chorionic villi
The chorion is the wall of the chorionic vesicle it is formed of 3 layers, the syncytiotrophoblast, the cytotrophoblast and the extra-embryonic mesoderm The chorionic vili start as primary vili the secondary vili then teritiary vili
51
Compare between placenta barrier before and after the 4th month
Before 4 months: - Syncytiotrophoblast - Cytotrophoblast - Extra-embryonic somatic mesoderm - Endothelium lining of capilaries After 4 months: - Syncytiotrophoblast - Endothelium of capilaries
52
Enumerate function of placenta
``` Nutrition Respiration Hormone production Barrier Transmission of maternal antibodies ```
53
Mention anomalies of placenta
``` Anomalies in position: -Placenta previa lateralis -Placenta previa marginalis - Placenta previa centralis Anomalies in attatchment to the umblical cord Anomalies in number -Placenta succenturiate -Placenta dipatita -Placenta tripatita -Placenta fenestrata -Placenta membranacea ```
54
Mention 4 types of equal conjoined twins
``` Craniopagus Thoracopagus Pyopagus Cranio-thoracopagus Union of trunk Rump-to-rump ```
55
Define unequal conjoined twins
One of the twins is large, called the host | The other twin is small, called the parasite
56
Superfoetation definition
Implantation of an extra blastocyst in a pregnant uterus
57
Superfecundation definition
Fertilization of more than one ovum by sperms from different males

Anatomy (8 decks)

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